Method For Storing And Transporting Arch-Shaped Stormwater Leaching Chambers

ABSTRACT

An improved method for storing and transporting arch-shaped stormwater leaching chambers includes positioning a group of nested chambers in an inverted “arch down” configuration upon a pallet to lower the center of gravity and stabilize the load, and using a pair of spaced cradle arms secured to the pallet to cooperatively position and support the palletized chambers against sideways rolling. Tie-down straps are then drawn through the natural saddle created by the inverted chambers and secured to the pallet, thereby reducing the required length and natural stretch of the straps over conventional methods. A lower center of gravity is therefore achieved, and load stability of the chambers is maximized during storage and transportation through more centralized weight distribution and an improved tethering system, thus reducing potential for injury and damage to the chambers during handling.

TECHNICAL FIELD

The present invention relates generally to the art of storing and transporting arch-shaped chambers used in stormwater and wastewater leaching applications. More particularly, the present invention pertains to an improved packing method which achieves a lower center of gravity and maximizes load stability of such chambers during storage and transportation, thereby improving handler safety.

BACKGROUND OF THE INVENTION

With ever-increasing hardcover being created by the continuing demand for commercial and residential development, natural absorption areas for stormwater and wastewater are becoming less available. For this reason, substantial efforts have heretofore been made to develop effective water management solutions which optimize the use of water and minimize the impact urban development has on the natural environment. In this regard, the use of underground corrugated plastic chambers for receiving and dispersing stormwater and wastewater into ground soil or other media have become well known in the art. Such chambers are generally molded to have arch shape cross sections with open bottoms and opposing sidewalls running upward from opposing side bases to the chamber crown (i.e., top). Each side base typically includes a flange which helps support the chamber on the media within which it is buried.

Substantial attention has been given in recent years to the nestability of such arch-shaped chambers, primarily due to the desire to optimize transportation and storage efficiency, and to reduce associated costs therewith. Since shipping and storage costs for such goods are dictated primarily by product volume, not weight, the greater the nesting density, the more economically the units can be shipped and stored. That is, improving nestability allows greater numbers of chambers to be stacked in a given height space.

However, increasing the number of stacked chambers can lead to significant safety issues involving the handling and transportation of such chambers. This is particularly true for larger sized chambers, where the chamber height can reach forty-five inches (45″) or greater, depending upon project requirements and/or needs of a particular application. Under current practices, as shown in FIG. 1 of the drawings, arch-shaped chamber units of this type are typically stacked for storage and transportation in an “arch up” configuration atop of chamber support members or platforms, such as pallets. Generally speaking, about 17-19 chambers can be nested and stacked upon each pallet, depending upon product configuration and height restrictions. In the “arch up” configuration, all of the weight of the nested chambers is dispersed along the two outside edges of the pallet. Consequently, when raised by a forklift, the central area of the pallet where the forks of the forklift typically engage have a tendency to deflect upwardly. This has been known to break the center of the pallet, thus creating a hazardous working condition. The more chambers stacked, the greater the chances are for the pallet to fail.

In addition to the above, by nesting the arch-shaped chambers in an “arch up” configuration, the center of gravity of the volume of bundled chambers becomes steadily higher, i.e., the more chambers stacked, the higher the center of gravity of the mass as a whole. Consequently, not only does the overall cumulative weight of the stacked bundle increase with more nested chambers, so does the height of the bundle's center of gravity. This makes the mass of bundled chambers as a whole top heavy and more unstable on their supporting pallet, thus leading to other potentially hazardous conditions both in the field and during transportation.

In order to help stabilize chambers being shipped in an “arch up” configuration, at least a pair of tether straps is typically crossed over the top of each chamber bundle (i.e., along the extrados surface of the arch) from one side of the pallet to the other. However, the more chambers that are stacked, the larger the bundle and the longer the straps need to be to cross over the bundle. With longer straps, there is more natural stretch of the straps once secured. Consequently, this can lead to a loosening of the straps, which further exacerbates an already unstable condition of secured cargo.

Consequently, it is evident there is a substantial need in the industry to improve the stabilization of such arch-shaped stormwater and wastewater leaching chambers during storage and transportation, so as to reduce the potential for injury and damage during handling and transport. In this regard, it is desirable to achieve a lower center of gravity of the bundled chambers to make the cargo less top heavy. To prevent bowing and overstressing the pallets, it is also desirable to distribute the weight of the chambers away from the pallet's outer edges and more toward the center where the cargo is typically hoisted by a forklift. Finally, shortening the length of the required tether straps securing the chambers to the pallets would also help to reduce the natural stretch and consequent loosening thereof during transport. These objects and more are achieved through the use of our improved method of chamber storage and transportation, as described more fully hereafter.

SUMMARY OF THE INVENTION

It has heretofore been considered conventional wisdom when palletizing most any cargo to maximize stability by spreading the weight of the cargo broadly across the entire surface area of the pallet. With regards to arch-shaped chambers utilized for stormwater and wastewater management, it has long since been considered standard practice to palletize such cargo for storage and transport in an “arch up” configuration. By so doing, a major portion of the weight of the chambers is transferred through the chamber sidewalls into the outer edges of the pallet, supposedly to maximize stability. However, for reasons presented above, this “arch up” configuration of stacking chambers has inherent drawbacks which can lead to unstable and hazardous handling conditions.

The present invention marks a stark departure from conventional practice in this regard. In accordance with the present invention, each chamber to be palletized is inverted from its normal “arch up” position, such that it opens upwardly with the crown of the chamber facing downward (i.e., “arch down”). In order to prevent the chamber(s) from rolling sideways on the pallet, the pallet is configured with a pair of spaced cradle arms which support the chamber(s) in their inverted position. The opposing cradle arms are cooperatively positioned and secured to the baseboards of the pallet so as to bear against the opposing sidewalls of the lowest chamber loaded on the pallet. Proper positioning of the cradle arms on the pallet will depend on the height of the cradle arms being used and the specific geometry of the chamber(s) being loaded on the pallet.

Loading chambers on a pallet in such an inverted “arch down” configuration provides a number of benefits for enhancing safety and reducing the potential for workplace injury and/or damage to the chambers. First, in an “arch down” configuration, the center of gravity of the load is greatly lowered, thus avoiding the load from becoming too top heavy and making the chambers safer to handle in all respects. Moreover, by inverting the chambers in this manner, all the downward force of the chambers now becomes directed toward the center of the pallet between the forks of the forklift, as opposed to the outer edges of the pallet in an “arch up” configuration. In this manner, the potential for the pallet breaking under the weight of the stacked chambers is greatly reduced.

In the “arch down” configuration, the cradle arms secured to the pallet function to support and prevent sideways rolling or tipping of the stacked chambers. In order to further stabilize the load, tethering or tie-down straps similar to those used in an “arch up” configuration are used to secure the load to the pallet. However, unlike the straps used for securing chambers stacked in an “arch up” configuration, the straps in an “arch down” configuration are not drawn transversely side-to-side across the entire arch (i.e., across the extrados surface) of the stacked bundle. Rather, the straps in an “arch down” configuration are drawn end-to-end through the natural saddle (i.e., along the intrados surface) created by inverting the chamber(s) on the pallet. By so doing, the straps used to secure the chambers require less overall strap footage. With less strap footage, the amount of natural stretch applied to the strap once secured is thus reduced, making the load more secure and safer to transport.

While the present invention has application to arch-shaped chambers of virtually all sizes, the benefits described above become greater for larger sized chambers. Taller and heavier chambers, when stacked, create larger overall loads with an increased mass and higher center of gravity. This is particularly true for arch-shaped stormwater and wastewater chambers having a height of approximately forty-five inches (45″) or greater. As provided above, with our improved method of packing such chambers, a lower center of gravity for the load is achieved and load stability of such chambers is maximized during storage and transportation through more centralized weight distribution and an improved tethering system. Handling of such palletized chambers in the field where rough terrain is frequently experienced will also be greatly improved, thereby improving handler safety. By utilizing our improved method for packing such arch-shaped chambers, injury and damage to chambers and individuals handling the chamber packs will be greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the invention will more fully appear from the following description, made in connection with the accompanying drawings, wherein like reference characters refer to the same or similar parts throughout the several views, and in which:

FIG. 1 is a digital photo showing the prior art method of stacking stormwater chambers in the conventional “arch up” configuration;

FIG. 2 is a digital photo showing an improved method of stacking stormwater chambers in accordance with the present invention, showing the side cradle arms supporting the chambers in an “arch down” configuration;

FIG. 3 is a digital photo showing stormwater chambers stacked in an “arch down” configuration as in FIG. 2, but showing an alternate cradle arm configuration to support the chambers on the pallet; and

FIG. 4 is a digital photo showing the manner in which straps are used in accordance with the present invention to secure the stacked stormwater chambers in an “arch down” configuration upon a pallet.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the following discussion, FIG. 1 shows a plurality of arch-shaped stormwater chambers 1 stacked as a nested bundle 3 upon a pallet 5 in the conventional “arch up” configuration. As noted above, conventional methods of stacking such chambers 1 in this configuration were derived from the belief that this would help maximize load stability by spreading the cargo weight broadly across the surface area of pallet 5. In this configuration, however, load stability is actually compromised as the number of stacked chambers increase.

By nesting multiple chambers in an “arch up” configuration, the center of gravity of the bundled chambers 3 as a whole rises significantly (i.e., several feet above the base of the pallet 5). With a substantial increase in mass as well, the bundle of chambers 3 become top heavy and more unstable during transportation, particularly on uneven terrain in the field. Moreover, by shifting weight distribution toward the outer edges 7 of pallet 5, the central area 9 where a forklift typically engages the pallet tends to bow and become weakened.

As shown further in FIG. 1, straps 11 made of steel or poly are typically used to secure the stacked chambers 3 to the pallet 5. Multiple straps 11 are generally used to secure each bundle of chambers 3. As seen, in the “arch up” configuration, the straps 11 are generally quite long and extend transversely side-to-side across the extrados surface of bundle 3, and around the entire bundle 3 and pallet 5. The larger the bundle 3 becomes, the longer the straps 11 need to be to cross over the bundle. The straps 11, however, have a tendency to stretch after tightening, and the longer the strap, the more susceptible the strap becomes to stretching and loosening. Consequently, it is not uncommon for straps 11 to loosen naturally over time, thus adding to an already unstable condition that could lead to other potentially hazardous conditions during transportation and in the field.

In order to resolve the deficiencies in the foregoing conventional storage and transportation methods, with the present invention each arch-shaped chamber 1 to be palletized is initially inverted to an “arch down” position on pallet 5. As shown in FIG. 2, in this position each chamber 1 opens upwardly, with the crown 13 of the chamber facing downward toward pallet 5 and the base 15 of the chamber 1 facing upward. As shown best in FIGS. 3 and 4, in the present “arch down” configuration, the chambers 1 are still capable of being nested together and stacked as a bundle of chambers 3 upon pallet 5, albeit in an inverted position. In this case, the lowermost chamber 1 is positioned with its crown 13 resting on the pallet 5 adjacent the center portion 9 thereof. Additional chambers 1 are then nested within the lowermost chamber 1 such that the extrados surface of each additional chamber 1 seats against the intrados surface of the next lower adjacent chamber 1 to form a stacked or bundled unit of nested chambers 3 upon the pallet 5.

As previously noted, loading chambers 1 on a pallet 5 in such an inverted “arch down” configuration provides a number of benefits for enhancing safety and reducing the potential for workplace injury and/or damage to the chambers. In an “arch down” configuration, the center of gravity of the bundled load of chambers 3 is greatly lowered, thus avoiding the load from becoming too top heavy and making the chambers safer to handle in all respects. Also, by inverting the chambers 1 in this manner, the downward force of the bundled chambers 3 is directed primarily toward the center 9 of the pallet 5 between the forks of the forklift, as opposed to the outer edges of the pallet 5 in an “arch up” configuration. In this manner, less reinforcement of the pallet 5 is required and the potential for the pallet 5 breaking under the weight of the stacked chambers is greatly reduced. Therefore, the load as a whole, including the pallet 5 and stack of chambers 3, becomes more stable and stronger as a unit.

In order to stabilize and prevent the bundle of chambers 3 from tipping or rolling sideways on pallet 5, the pallet is configured with a pair of spaced anti-tipping restraints or cradle arms 17 which support the chamber(s) 1 in their inverted position. As shown in FIG. 2, the opposing cradle arms 17 are firmly secured to the baseboards of the pallet 5 and extend parallel with the length on the chambers loaded on pallet 5. The cradle arms 17 may extend partially or completely the length of the bundle of chambers 3 from end to end. The cradle arms 17 are cooperatively positioned so as to bear against the outer surface of the opposing sidewalls of the lowest chamber 1 loaded on the pallet 5.

Proper positioning of the cradle arms 17 on pallet 5 will depend on the configuration and height of the cradle arms 17 being used, and the specific geometry of the chamber(s) being loaded on the pallet 5. In one embodiment, as shown in FIG. 2, each of the cradle arms 17 may be formed as a pair of upstanding brace assemblies (17A, 17B). In this embodiment, each brace assembly (17A, 17B) includes a pair of base runners 19 to which a plurality of angled support members 21 are secured in upright orientation. As shown, each support member 21 has a tapered edge 23 which angles upward and outward away from the central area of pallet 5 at a pitch which approximates a tangential slope of the bottom chamber 1 loaded on pallet 5. An elongated support panel 25 spans across and is connected to the tapered edge surface 23 of each support member 21 adjacent the upper end thereof. Opposing brace assemblies (17A, 17B) are therefore constructed such that the support panel 25 of each bears substantially flat against the outer arcuate surface of the bottom chamber 1.

In the embodiment of FIG. 2, the support panels 25 of each brace assembly (17A, 17B) bear against the opposing sidewalls of the lower chamber 1 at an elevated point 27 from the base of the pallet 5. In this embodiment, the point at which the support panels 25 engage the sidewalls of the chamber 1 is well above the center of gravity of the inverted chamber 1, and chamber 1 is therefore well supported against possible sideways tipping or rolling. However, as more chambers 1 become nested and stacked, the center of gravity of the resulting bundle of chambers 3 may approach or exceed the cradle arm point of engagement 27, thus potentially impacting the stability of the load.

In order to provide additional stability to a bundled load of chambers 3, tethering or tie-down straps 29 may be used to secure the load firmly to the pallet 5. As best shown in FIGS. 3 and 4, tie-down straps 29 are similar in construction to those used in an “arch up” configuration. However, in an “arch down” configuration, straps 29 provide improved stabilization due to the manner in which they secure the load of bundled chambers 3 to the pallet 5. As shown in FIGS. 3 and 4, tie-down straps 29 may be drawn end-to-end through the natural saddle 31 (i.e., along the intrados surface) created by the bundle of inverted chambers 3 on pallet 5. Consequently, tie-down straps 29 are much shorter than the straps 11 used in an “arch up” configuration (which extend transversely side-to-side across the entire extrados surface or external arch of the bundled chambers), and are therefore less susceptible to loosening over time due to the natural stretch in the strap material. As shown, each strap 29 is drawn across the central saddle area 31 on the intrados surface adjacent the crown 13 of the uppermost chamber 1 of the bundled nest 3, and angled outwardly therefrom toward the opposite outer edges of pallet 5. Protective members 37 may be inserted between the tethering straps 29 and bundle of chambers 3 to help secure and protect the chambers when secured to the pallet 5. Therefore, upon tightening the straps 29, the bundle of chambers 3 is drawn firmly against both pallet 5 and the opposing cradle arms 17 positioned on each side of the load. By securing the load in this way, the bundled stack of chambers 3 is secured to the pallet 5 between the supporting cradle arms 17 using less strap footage, thereby effectively reducing the amount of natural stretch and making the load more secure and safer to transport.

Of course, other cradle arm configurations and/or anti-tipping restraint designs may be used and are contemplated to be within the scope of the present invention. Such anti-tipping restraints must be designed and function to at least support a plurality of nested arch-shaped chambers 1 stacked as a bundled load 3 upon pallet 5 in an “arch down” orientation, so as to prevent side-to-side rolling or tipping of the chambers during storage and transportation. One such alternative embodiment is shown in FIG. 4, where, instead of the brace assemblies (17A, 17B) shown in FIG. 2, the cradle arms 17 are constructed as a pair of elongated runners 33. As shown, the runners 33 are cooperatively spaced on pallet 5 based on the size and configuration of the arch-shaped chambers 1 loaded thereon. The chamber size and relative thickness/height of each runner 33 dictate the positioning of the runners 33 on pallet 5. On each opposite side of the stack of chambers 3, a runner 33 is wedged between the base of pallet 5 and the outer surface of the bottom chamber 1. Runners 33 are fixedly secured to the base of the pallet 5 in such positions as to bear firmly against the outer surface of the bottom chamber 1 resting on pallet 5.

Here again, as shown in FIG. 4, in order to provide additional stability to a bundled load of chambers 3, tethering or tie-down straps 29 are preferably used to secure the load firmly to pallet 5. Particularly with the use of runners 33, where the center of gravity of the bundle of chambers 3 may be significantly higher than the point of runner engagement 35 therewith, the use of straps 29 are beneficial to further stabilize the load upon the pallet. As previously discussed, each strap 29 is drawn across the central saddle area 31 of the uppermost chamber and angled outwardly therefrom toward the opposite outer edges of pallet 5, making such straps 29 much shorter and less susceptible to loosening than the straps 11 used in an “arch up” configuration. Upon tightening the straps 29, the bundle of chambers 3 is then drawn firmly against both pallet 5 and the opposing runners 33.

With the present method, the crown of the lowest chamber 1 stacked on the pallet is positioned such that it is seated on the pallet 5 at or near the center 9 of the pallet. Additional chambers may then be added as desired by nesting one inverted chamber within another. The cradle arms 17 may be located on the pallet 5 in such position that they begin to engage the outer surface of the chamber sidewalls at or closely adjacent to the point where the crown 13 of the lowermost chamber 1 comes into engagement with the top of the pallet baseboards, similar to that shown in FIG. 4. Depending on the size and configuration of the stack of chambers 3, increased stability can be obtained with a more robust cradle arm structure 17, similar to that shown in FIG. 2. The added structure of the cradle arms 17 also helps to strengthen the pallet adjacent the area where the forklift lifts the load. Similar to the “arch up” configuration, in the “arch down” configuration, additional chambers 1 may still be nested and stacked as a bundled unit 3 upon a pallet 5, but the center of gravity of the bundled unit 3 remains much lower and closer to the base of the pallet 5.

As noted above, the benefits described above become even greater for larger sized chambers. Taller and heavier chambers, when stacked, create larger overall loads with an increased mass and higher center of gravity. This is particularly true for arch-shaped stormwater and wastewater chambers having a height of about forty-five inches (45″) or greater measured between the open bottom base 15 and crown 13 thereof. As provided above, with our improved method of packing such chambers, a lower center of gravity for the load is achieved and load stability of such chambers is maximized during storage and transportation through more centralized weight distribution and an improved tethering system. Handling of such palletized chambers in the field where rough terrain is frequently experienced will also be greatly improved, thereby improving handler safety. By utilizing our improved method for packing such arch-shaped chambers, injury and damage to chambers and individuals handling the chamber packs will be greatly reduced.

The disclosure herein is intended to be merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the invention herein, which comprises the matter shown and described herein and set forth in the appended claims. 

What is claimed is:
 1. A method of lowering the center of gravity of a nested bundle of arch-shaped chambers for storage and transportation, comprising the steps of: providing a plurality of chambers, each chamber having an arch-shaped cross section geometry with an open bottom and opposing sidewalls extending upwardly from the open bottom to a chamber crown, wherein the plurality of arch-shaped chambers are configured to be nested together for storage and transport; providing a chamber support member with a base and a pair of cradle arms secured to the base for supporting the plurality of chambers thereon; inverting one of the plurality of chambers and positioning it as a first chamber upon the support member such that its open bottom faces upward and its crown faces downward against the base of the support member, with one of the pair of cradle arms bearing against each opposing sidewall of the first chamber for support thereof; and inverting each of the remaining plurality of chambers such that its open bottom end faces upward and its crown faces downward, and nesting the remaining plurality of chambers together with the first chamber in an inverted position as a stacked unit upon the support member.
 2. The method set forth in claim 1, including the step of securing the plurality of inverted chambers to the support member with a tethering device.
 3. The method set forth in claim 2, wherein each of the plurality of chambers has an intrados and extrados surface defined by its arch-shaped geometry, and the tethering device bears against the intrados surface of an uppermost nested chamber of the stacked unit.
 4. The method set forth in claim 3, wherein the step of securing the plurality of inverted chambers to the support member includes drawing the tethering device along the intrados surface of the arch-shaped geometry of the uppermost nested chamber of the stacked unit between opposite ends of the plurality of chambers and securing the tethering device to the support member.
 5. The method set forth in claim 3, wherein the tethering device is seated against the intrados surface of the uppermost nested chamber adjacent the crown thereof.
 6. The method set forth in claim 1, wherein the step of providing a support member with a pair of cradle arms includes spacing the cradle arms on the support member appropriately such that each cradle arm bears against an extrados surface of one of the opposing sidewalls of the first chamber.
 7. The method set forth in claim 6, wherein each cradle arm includes a planar bearing surface which is adapted to engage an extrados surface of one of the opposing sidewalls of the first chamber.
 8. The method set forth in claim 1, wherein the step of providing a support member with a pair of cradle arms includes positioning the cradle arms such that the crown of each of the plurality of chambers is positioned along a vertical plane near the center of the chamber support member.
 9. A method of lowering the center of gravity of a nested bundle of arch-shaped chambers for storage and transportation, comprising the steps of: providing a first chamber having an arch-shaped cross section geometry with an open bottom and opposing sidewalls extending upwardly from the open bottom to a chamber crown; inverting the first chamber such that its open bottom faces upward and its crown faces downward; positioning the inverted first chamber upon a chamber support platform between a pair of spaced anti-tipping restraints such that the anti-tipping restraints bear against the opposing sidewalls of the first chamber to prevent the first chamber from rolling or tipping sideways on the support platform; nesting at least one additional chamber having an arch-shaped cross section geometry with the first chamber such that an extrados surface of each additional chamber seats against an intrados surface of an adjacent chamber to form a stacked unit of nested chambers upon the chamber support platform; and securing the stacked unit of nested chambers to the chamber support platform with a tethering device, wherein the tethering device is seated against the intrados surface of an uppermost nested chamber.
 10. The method set forth in claim 9, wherein the step of securing the stacked unit of nested chambers to the chamber support platform with a tethering device includes drawing the tethering device between opposite ends of the nested chambers and securing the tethering device to the support platform adjacent each of the opposite ends.
 11. The method set forth in claim 9, wherein the tethering device is seated against the intrados surface of the uppermost nested chamber adjacent a crown portion thereof.
 12. The method set forth in claim 9, wherein the step of positioning the inverted first chamber upon a chamber support platform includes configuring each of the anti-tipping restraints with a planar bearing surface which is adapted to engage an extrados surface of one of the opposing sidewalls of the first chamber.
 13. The method set forth in claim 9, wherein the step of positioning the inverted first chamber upon a chamber support platform includes configuring each of the anti-tipping restraints as an elongated support arm that is affixed to the chamber support platform.
 14. The method set forth in claim 13, wherein each support arm extends substantially to length of the first chamber between opposite ends thereof.
 15. The method set forth in claim 9, wherein the step of positioning the inverted first chamber upon a chamber support platform includes positioning the anti-tipping restraints such that the crown of the inverted first chamber is positioned along a vertical plane near the center of the chamber support member.
 16. The method set forth in claim 9, wherein the height of the first chamber and at least one additional chamber extending between an open bottom base and the crown thereof is about 45 inches or greater.
 17. A method of lowering the center of gravity of a nested bundle of arch-shaped chambers for storage and transportation, comprising the steps of: providing a first chamber having opposite chamber ends and an arch-shaped cross section geometry of approximately 45 inches in height or greater extending between an open bottom base and a chamber crown, and opposing arcuate sidewalls extending upwardly from the open bottom base to the crown; inverting the first chamber such that its open bottom base faces upward and its crown faces downward; positioning the inverted first chamber upon a chamber support platform between a pair of spaced elongated cradle arms such that the cradle arms bear against the opposing sidewalls of the first chamber to prevent the first chamber from rolling or tipping sideways on the support platform; nesting at least one additional chamber having opposite chamber ends and an arch-shaped cross section geometry with the first chamber such that an extrados surface of each additional chamber seats against an intrados surface of an adjacent chamber to form a stacked unit of nested chambers upon the chamber support platform; and drawing a tethering strap between the opposite chamber ends of an uppermost chamber of the stacked unit of nested chambers and securing the tethering strap to the support platform such that the tethering strap exerts a restraining force against an intrados surface of the uppermost nested chamber.
 18. The method set forth in claim 17, wherein each cradle arm extends substantially to length of the first chamber between the opposite ends thereof.
 19. The method set forth in claim 17, wherein the step of positioning the inverted first chamber upon a chamber support platform includes configuring each of the cradle arms with a planar bearing surface which is adapted to engage an extrados surface of one of the opposing sidewalls of the first chamber.
 20. The method set forth in claim 17, wherein the step of drawing the tethering strap between the opposite chamber ends of the uppermost chamber of the stacked unit of nested chambers includes tightening the tethering strap to exert a restraining force against the intrados surface of the uppermost nested chamber adjacent a crown portion thereof. 